Apparatus for testing golf clubs

ABSTRACT

An apparatus for testing the dynamic performance of a golf club by simulating human golf swings including an arm driven by a first motor for simulating the rotation of the golfer&#39;&#39;s arms about his body and a club holder driven by a second motor for simulating the rotation of the golfer&#39;&#39;s wrists about his arms. The arm and club holder may be driven independently.

ite States [111 3,855,842 1451 Dec. 24, 1974 Imabori et al.

[ APPARATUS FOR TESTING GOLF CLUBS [75] Inventors: Junpei imabori,Nishinomiya;

Takeshi Kuzuoka,'l(obe; Atsuhiko Mori, Osaka, all of Japan [73]Assignee: Sumitomo Rubber Industries, Ltd.,

Kobe-shi, Kyogo, Japan [22] Filed: May 16, 1973 [21] Appl. No.: 361,005

[30] Foreign Application Priority Data May 24, 1972 Japan 47-51351 [52]US. Cl. 73/13 7 3/432 SD [51] Int. Cl. "L G0lm 3/00 [58] Field ofSearch... 73/432 SD, 65, 13;

273/186 A; 35/29 A;v

[56] References Cited, v

UNITED STATES PATENTS 2/1929 Mesple 35/29 A ShubertW, 73/13 FOREIGNPATENTS OR APPLICATIONS 39 ,123 8/1933 Great Britain 35/29 A OTHERPUBLICATIONS S. W. Herwald, Fundamentals of Servomechanisms How toSelect and Apply Them, June 1946, 7 pages.

Primary Examiner-Richard C. Queisser Assistant ExaminerAnthony V.Ciarlante Attorney, Agent, or FirmSughrue, Rothwell, Mion, Zinn &Macpeak 57] ABSTRACT An'apparatus for testing the dynamic performance ofa golf club by simulating human golf swings including an arm driven by afirst motor for simulating'the rotation of the golfers arms about hisbody and a club holder driven by a second motor for simulating therotation of the golfers wrists about his arms. The arm and club holdermay be driven independently.

2 Claims, 10 Drawing Figures PAIENIED 3.855.842 SHEEIIILFQ ANGLE OFROTATION PATEM 052241974 3,855,842 sum 3 95 '3 FIG. 8

CLOCK PULSE E FIG. 9

5 30 C E"-.- R E B r I 8 FIG. I0

I PROGRAMME-D i-PO'SITION "*1 (9)-SlGNAL SWING l J CLOCKrPULSE v 1POTENTIOMETER j PROGRAMMED SIGNAL POSITION T INPUT GENERATOR ERV Y T MCLUB APPARATUS FOR TESTING GOLF CLUBS BACKGROUND OF THE INVENTION 1.Field of the Invention The present invention relates to an apparatus fortesting the dynamic characteristics of a golf club by swinging of thegolf club in a manner simulating swing patterns of human golf players.

2. Description of the Prior Art It is necessary in designing golf clubsfor higher quality to test the dynamic efficiency or a property of agolf club which is appropriate for a particular swing form or pattern.This is because there are so many swing patterns among different golfplayers. For test purposes, absolutely identical swing patterns shouldbe repeated. However, this requirement cannot be fully met by the humangolf players because the reproducibility of a particular swing patternis poor. Another difficulty resides in that one test player can presentonly. one swing pattern at the most, and as such it is impossible toattain a variety of swing patterns.

SUMMARY or THE INVENTION According to the present invention, thedifficulties encountered in testing golf clubs are eliminated, and awide variety of swing patterns simulating those of human players areautomatically obtained withcomplete and exact reproducibility.

Swinging motion, more specifically the downswing, of a golf club iscomposed of two motions: one is a rotational motion performed by aplayer in a plane inclined relative to the horizontal and including anover-head position in which the club-head is over the players head withhis body fully wound up and a hitting position in which the club-headjust approaches-impact with the golf ball with the players bodyuncoiled. The other motion is also a rotational motion performed in theabove plane concurrently with the former motion but its center ofrotation is located at the moving wrists of the player. The apparatusaccording to the invention correctly simulates and puts the above tworotational motions into effect.

The main feature of the present invention resides in an apparatus fortesting the dynamic efficiency of a golf club comprising an arm portionand a club-grip holder both adapted to firmly hold the grip of a golfclub and to swing independently of each other with respect to arelatively stationary main body so that the golf club is caused toexperience the composed swinging motion with respect to the twodifferentcenters of rotation; and driving means responsive to anelectric control signal for effecting the independent swinging motionsof the arm portion and of the club-grip holder.

The apparatus according to the invention is thus composed of amechanical portion adapted to set a golf club and to cause the same toswing, and of an electric control portion adapted to effect the swingingmotion of the golf club in a fashion to simulate a variety of swingpatterns of human golf players.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of anapparatus for testing dynamic characteristics of a golf club accordingto the invention.

FIG. 2 is a cross-sectional view taken along the line AA of FIG. I.

FIG. 3 is an enlarged perspective view of an embodiment of a golf clubgrip holder as used in the apparatus of FIG. 1.

FIG. 4 is an explanatory view showing analyzed swing angles of a golfclub when a human player makes a downswing of the club.

FIG. 5 shows characteristic curves of the swing angles of FIG. 4 whichare plotted against time during the time interval between the initiationof the downswing and the instant of impart with a golf ball. I

FIG. 6 is a block diagram showing a programmed signal generator usedwith a mechanical portion of the apparatus of FIG. I. I

FIG. 7. is similar to FIG. 6 but shows a displacement servo system asused-with the signal generator of FIG. 6.

FIG. 8 is a graph showing the waveforms occuring in certain portions ofFIG. 6.

FIG. 9 is a schematic diagram of the poteneiometer shown in FIG. 7.potentiometer FIG. 10 is a block diagram of the electric control portionof the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT member 19 which is threaded forlocking the position of the apparatus. A tilting handle 8 is mounted onthe upper end of the supporting post 9 and is manually turned forcontrolling the inclination of the motor casing 7 with respect to thehorizontal. 7

Turning now to FIG. 2, two electric motors M and M are installed withinthe motor casing 7.Two pulleys 14 and 15 are rotatably mounted on shaft21 driven by the motor M, and an arm portion 5 is secured to theextending end of shaft 21. The pulleys 14 and 15 may be preferablyintegral or coupled with each other so as to rotate simultaneously. Apulley 13 is secured to a shaft 27 driven by the motor M 1 A club-gripholder 4 and a pulley 12 are secured respectively to a shaft 22 on theoutside and inside of a casing 6 of the arm portion 5. Two endless belts17 and 16 are respectively between pulleys l3 and 15 and between pulleys14 and'12.

With this construction, the driving force of the motor M is deliveredfrom the pulley 13 through the pulleys 15 and 14 to the pulley 12, thusrotating the shaft 22. This rotational motion is then applied to thegrip holder 4 and accordingly to a golf club which includes a gripportion 3, shaft portion 2 and head portion 1. The golf club is fastenedin advance to the grip holder 4. The

club is caused to swing about the shaft 22 which corresponds to thecenter of rotation of the players wrists. The driving force of the motorM is directly delivered to the arm portion 5 through the shaft 21, whichcorresponds to the center of rotation of the players body. Thus, thegolf club can swing with the two centers of rotation independent of eachother. Therefore, it will be easily understood that a variety of desiredswing patterns, correctly simulating those of human players, are

obtainable if the motors M M are properly controlled.

As shown in FIG. 3, the grip holder 4 is composed of two similar plates24 respectively having a groove of semicircular cross-section sized toreceive the grip portion 3 of the golf club-After having interposed thegrip portion 3 between the grooves, the mating plates 24 are clamped bya suitable locking means such as a plurality of bolts 23.

The operation of the mechanical portion of the apparatus is electricallycontrolled by an electric control portion in a manner as will beexplained in the following. In order to attain a wide variety of swingpatterns correctly simulating those of human golf players, the rotationof the motor M should closely simulate the movement of the playerswrists, while the rotation of the motor M should closely simulate theswinging motion of a golf club with respect to the moving wrists.

For these simulating purposes, the movement of the wrists or arms andthe swinging motion of the club both during the downswing arediagrammatically analyzed in a manner as shown in FIG. 4. Here, let itbe assumed that the angles of rotation taken by both of the players armsand of the club relative to the players wrists during a time intervalbetween the initiation of the downswing and the impact of the club headwith a golf ball are respectively denoted by 6 and 4). These two angles6 and d) are converted into electric signals, which in turn areintroduced into respective programmed signal generators, one of which isillustrated in FIG. 6. A programmed signal thus produced in a generatoras a volt age signal is then delivered to a servo-amplifier, an SCRtrigger unit (phase control) and an SCR unit electrically connected toan AC. power source as shown in FIG. 7. The output of the SCR unit isapplied to the corresponding motor M, or M to effect the rotationaloperations in a finely controlled fashion. The controlled rotations ofthe motors will lead to the swinging motion ofa golf club, as has beendescribed. The swinging motion thus obtained is observed by suitablepotentiometers, one of which is shown in FIG. 7. Each potentiometerconverts the characteristics of its associated motion into a voltagesignal which in turn is fed back to the servo-amplifier and comparedthere with the programmed signal to produce an error signal which causesthe motor to follow the programmed signal. In this way, inconsistency iseliminated between the obtained swinging motion and the simulated motionexpected to be obtained in accordance with the input signalscorresponding to the angles and d).

A programmed signal generator, as shown in FIG. 6, can preset a desiredangle of rotation in terms of electric potentials (E E E;,, E, E whichare determined by resistance levels of a potentiometer corresponding toa number of segments of the time interval as previously defined. Thepreset potentials are then applied in consecutive order of the segmentaltime intervals so that a stepped waveform resembling a desired curve(see FIG. which indicates the angle of rota-. tion plotted against timeduring the downswing, may be obtained. With reference to FIG. 6, morespecifically, a stepped waveform signal is transmitted into an automatic tangent determining circuit, formed by the subtraction integratorand sample-and-hold circuit, to produce a tangential waveform resemblingthe particular curve.

FIg. 8 illustrates the waveforms present at points A, B, C and D in FIG.6.

Waveform C indicates the value of a prior step of waveform B immediatelyafter a clock pulse. Since the sample and hold circuit samples and holdsthe value of the waveform c, the value of waveform D is kept constantuntil the following sample instruction or clock pulse occurs, even ifthe value of waveform C varies in accordance with the lapse of time.Accordingly, the difference between the inputs B and D in thesubtraction integrator is the difference in height of the steps at thepreceding and following clock pulses. The slope or tangent of theintegrated output C is directly proportional to the difference between Band D, and the value of C equals the value of B immediately before thefollowing clock pulse. Though being constant, the period of the clockpulse is increased twice or ten times for a slowmotion swing. Therefore,the integrating constant of the subtraction integrator may be changed byinterlocking it with the change-over switch for slow-motion.

Referring to FIG. 7, the servo-amplifier may preferably be used with acontrol element of the SCR type, in which the three phase electricenergy is supplied from the power source and rectified. With use of thisSCR system, the electric control portion can feed a control signal ofsufficiently high voltage and of sufficiently high instantaneouselectric current to the mechanical portion, especially the motors.However, this SCR system is not necessarily indispensable; other controlunits using electronic elements such as transistors may be used forrectifying the high three phase electric energy. In order to improveresponsiveness of the apparatus, it may be preferable to increase thefrequency of the power source. Moreover, the motors may preferably beused with a reduction unit to minimize the resultant inertia.

A detailed description will now be made of the ernbodiment of thepresent invention in which the SCR control system of FIG. 7 was employedfor rectifying the electric energy of the three-phase power source. Thepower source used was of the type having the maximum voltage of 180volts, the maximum instantaneous current of amperes, and a frequency of400 Hz. If, however, a suitable generator is obtainable as the powersource, the output frequency may preferably exceed I000 Hz. The motorsused were of a minimum inertia type motor, made by Yasukawa ElectricCompany, Ltd., which was designed to minimize the moment of inertia ofthe rotor. The motor M, for controlling the angle 6 had the maximuminstantaneous torque of 2.5 kg.m and was used in combiantion with areduction gear unit having a reduction ratio of 1/17. The motor M forcontrolling the angle 4) had a maximum instantaneous torque of 1.3 kg.mand a reduction gear unit having a reduction ratio of l/ l 1. Since bothof the angles 0 and d) were controlled within a range of 200, thefeed-back detector used for observing each of the obtaining swing motionwas a potentiometer of the type controlled by a single turn of itsshaft. The SCR trigger unit was a thyristor gate FS 3G 24-B, made byNippon Electric Co. The manner in which an SCR unit is triggeredrelative to the phase of an applied A.C. wave to control the powerapplied to a motor is well known. The embodiment as describedhereinbefore revealed that the apparatus according to the presentinvention can produce the desired result.

FIG. 9 schematically illustrates one form of potentiometer which maybe'used to observe the actual swinging motion of the club.

The motor shaft 21 of arm portion 5 and the motor shaft 22 of the gripholder 4 are respectively coupled directly to the rotating slidingcontact 30 of the potentiometer either directly, or indirectly through anon-slip belt, for example. Consequently, the angle of rotation of theslider contact 30 corresponds exactly to that of motor shafts 21 and 22.

In the schematic diagram of FIG. 9, a constant voltage E. is applied tothe terminals A and B. When the sliding contact connected to output.terminal C traverses the resistance R in accordance with the angle a ofrotation of a driving shaft, the resistance value r between terminal Bor B and terminal C is directly proportional to the angle Accordingly,the voltage e between terminals C and B becomes e r/R X E; i.e. voltagee is proportional I to the angle a; or as applied to this invention, thevoltage e is proportional to the rotating angle 6 of the shaft 21 or armportion 5 or to the rotating angle 11) of the shaft 22 of the club-gripholder 4.

FIG. is a block diagram illustrating the manner in which theproportional signal generators (FIG. 6) and the SCR control systems(FIG. 7) are interconnected to form the complete electriccontrol portionof the invention.

Since the apparatus of the invention employs programmed signals forcontrolling the operations of the mechanical portion, the change of theswing angles during the time interval of the downswing can be set morefreely within its maximum angular displacement and acceleration than inthe conventional automatic testing apparatus of a purely machanicaltype. Moreover, the swing angle change can be easily performed byturning a set dial, thus providing for a wide variety of programmedswing patterns. The electric control portion of the apparatus issupplied with voltage signals dictated by the programmed angle changesduring the time interval, and includes so-called displacement servosystems in which the resultant angular displacements of the golf clubclosely follow the commanding voltage signals. As a result, theprogramming can be carried out without any complicated calculation, andas such a servo system is considerably better than a conventionalpneumatic servo system which is very complicated. It should beunderstood that the source of driving force is not limited to the DC.motor as used in the example but may be a hydraulic pressure motorcontrolled by an electric signal. In addition, the apparatus of theinvention may desirably be used with a photoelectric pick-up devicewhich is positioned in the vicinity of the impact point of a golf ballso as to detect and record the velocities of a golf club and the ballboth at the instant of the impact.

While the invention has been particularly shown and described withreference to the preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

We claim:

.1. An apparatus for testing dynamic characteristics of a golf club,said apparatus comprising:

ond program signals to said first and second drive I means,respectively, whereby said drive means are controlled independently ofeach other by said program signals so that a plurality of golf clubswing patterns may be simulated by the combination of independentoperations of I said first and second drive means.

2. The apparatus as set forth in claim 1 wherein each of said first andsecond drive means comprises:

a. potentiometer means coupled to the associated drive means forproducing a position signal indicative. of the actual angle of rotationof the drive means; and

b. servo-amplifier means for receiving and comparing correspondingprogram and position signals to produce an error signal which causes thedrive means to assume the actual position called for by the.

value of the program signal.

1. An apparatus for testing dynamic characteristics of a golf club, saidapparatus comprising: a. a main body; b. arm means rotatably mounted onsaid main body, said arm means swinging relative to said main body; c.club holder means for holding said golf club and rotatably mounted onsaid arm means, said club holder means rotating relative to said armmeans; d. first drive means for rotating said arm means independently ofsaid holder means; e. second drive means independent of said first drivemeans, for rotating said holder means independently of said arm means;and f. signal generator means for applying first and second programsignals to said first and second drive means, respectively, whereby saiddrive means are controlled independently of each other by said programsignals so that a plurality of golf club swing patterns may be simulatedby the combination of independent operations of said first and seconddrive means.
 2. The apparatus as set forth in claim 1 wherein each ofsaid first and second drive means comprises: a. potentiometer meanscoupled to the associated drive means for producing a position signalindicative of the actual angle of rotation of the drive means; and b.servo-amplifier means for receiving and comparing corresponding programand position signals to produce an error signal which causes the drivemeans to assume the actual position called for by the value of theprogram signal.